Liliang Chen

Wurtzite-type ZnS nanoparticles by pulsed electric discharge

The synthesis of wurtzite-type ZnS nanoparticles by an electric discharge submerged in molten sulfur is reported. Using a pulsed plasma between two zinc electrodes of diameter 5 mm in molten sulfur, we have synthesized high-temperature phase (wurtzite-type) ZnS nanocrystals with an average size of about 20 nm. The refined lattice parameters of the synthesized wurtzite-type ZnS nanoparticles were found to be larger than those of the reported ZnS (JCPDS card no 36-1450). Synthesis of ZnMgS (solid solution of ZnS and MgS) was achieved by using ZnMg alloys as both cathode and anode electrodes. UV-visible absorption spectroscopy analysis showed that the absorption peak of the as-prepared ZnS sample (319 nm) displays a blue-shift compared to the bulk ZnS (335 nm). Photoluminescence spectra of the samples revealed peaks at 340, 397, 423, 455 and 471 nm, which were related to excitonic emission and stoichiometric defects.

Effect of shock compression on wurtzite-type ZnMgS crystals

It is hard to generate twin defects in wurtzite-type ZnMS (M: metal element) crystals by static mechanical method, while it is important for the luminescence. It was found that many twin defects were formed in wurtzite-type ZnMgS crystals by shock compression of >15 GPa in stress, and the absorption and luminescence spectra changed.

Synthesis of wurtzite-type ZnMgS by the pulsed plasma in liquid

Wurtzite-type ZnMgS (w-ZnMgS) nanoparticles were synthesized using the pulsed plasma in liquid method. By the pulsed plasma generated between two electrodes made of ZnMg alloy in liquid sulfur, we produced w-ZnMgS nanocrystals mixed with Zn2Mg and MgS. Higher purity w-ZnMgS sample was achieved by annealing at 773 K. The synthesized ZnMgS nanoparticles were of spherical shape and contained of many crystal defects (stacking faults). Ultraviolet?visible (UV?vis) absorption spectroscopy analysis of the synthesized w-ZnMgS showed absorption edge broadening and appearance of a small absorption band at around 400 nm even without doping.

Synthesis of WO3·H2O nanoparticles by pulsed plasma in liquid

Pure orthorhombic-phase WO3·H2O nanoparticles with sizes of about 5 nm were synthesized by pulsed plasma in deionized water, in which tungsten electrodes provide the source of tungsten and the water is the source of oxygen and hydrogen. The quenching effect and liquid environment inherent in this pulsed plasma in liquid method resulted in ultra-small particles with lattice lengths (a = 5.2516 A, b = 10.4345 A, c = 5.1380 A) larger than those of reference lattices. The emission lines of W I atoms, W II ions and H I atoms were observed by an optical emission spectrum in order to gather information on the synthetic mechanism. These nanoparticles showed higher absorption in the visible region than did ST-01 TiO2 and Wako WO3 nanoparticles. The WO3·H2O nanoparticles displayed more activity in the photocatalytic test than did the commercial TiO2 sample (ST-01). Also, the absorption edge of WO3·H2O shifted to longer wavelengths in the UV-Vis absorption pattern relative to that of the anhydrous tungsten oxide.